Refining of nonferrous metals



June 16, 1942. J STACK 2,286,240

REFINING OF NON-FERROUS METALS Filed March 21, 1938 v s Sheets-sheaf, 1

FIG. I.

CRUDE COPPER ANODES ELECTROLYTIC DEPOSIT/0N OF COPPER FROM AN STEPAROMATIC SULPHO/V/C AC/D ELECTROLYTE COPPE R CA THODES ANODE 5L IMESFOUL ELECTROLYI'E COPPER REMOVED BY ELECTROLYSIS AND PRECIPITATION WITHTIN OR LEAD STEP 2* l PPT'ED COPPER 7'0 CRUDE ANODES PUR/F IE Dl E LE C7' ROLY TE COPPER CA THODES LEAD AND T/N REMOVED STEP BY ELECTROLYS/SSOLDER CA 7710055 L/OUOR ZINC AND NICKEL REMOVED STEP 4 BYCRKSTALlZAT/ON AS 5 UL PHONA TE REGENERA TED FREE ZINC AND NICKEL SULPHONATES ACID RETURNED r0 RCCRYCI'ALL/ZEQPPI'CD mrH LIME PREPA RA r/0/v0F E L E C TROL Y TE 1 CALCIUM .SUL PHONA r5 ZINC REMOVED FROM SOLUTIONWORKED UP PPTED HYDROx/DES r0 RECOVER 14cm WITH CAusr/C SODA l SOD/UMZ/NCAT'E SOLUTION ELECTROLYZED 7'0 RECOVER ZINC I Z/Nc CAT/10055 NICKELHYDROX/DE DISSOLVED m/ AMMONIA AND NICKEL RECOVERED Br 5/. ECTROLYS/SINVENTOR J. R STACK NICKEL CATHODES By June 16, 1942.

COPPE R CA T HODE S STEP 2 LEAD .S'ULPHATE STEP 3* J. R. STACK REFININGOF NON-FERROUS Filed March 21, 1958 FIG. 2.

METALS 3 Sheets-Sheet 2 CRUDE COPPER ANODES ELECTROLYIIC DEPOSITION OfCOPPER FROM AN A ROMA T/ C 5 UL PHONIC ACID ELECTROL YTE ZINC RECOVEREDAS IN FIG. I.

FOUL ELECTROLYTE IANODE SLIMES LEAD PPTED WITH QUANTITATIVE AMOUNT OFSULPHUR/C ACID L/OUOR COPPER A ND TIN DE POS/ TE D ELECTROLYT/CALL YLIQUOR NICKEL mo/v AND ZINC PPTED WITH L/ME ZINC REMOVED BI LEACH/NGWITH CAUSTIC SODA NICKEL RECOVERED IN FIG.

CA THODES A ND SLUD GE 70 CRUDE COPPER A NODES CALCIUM SULPHONA rEREGENERA rEo r0 EREE SUL PHON/C ACID T0 BE RETURNED TO ELEcmoLrrEMETALLIC ZINC ME'mLL/c NICKEL RES/DUES TO WASTE INVENTOR TACK REFININGOF NON-FERROUS METALS Filed March 21, 1938 5 Sheets-Sheet 3 FIG. 3.

ROASTED PULVER/ZED AND LEACHED WITH SULPHON/C ACID LIQUORS RETURNED 7'0ELECTROLKTE of FIG. I.

SMELTED T0 METAL AND CAST AS ANODES TIN AND LEAD REMOVED BY ELECTROLYS/S/N SULPHON/C ACID ELECT/POLY? E rnv 02 501.059

c4 THODS A NODE SL/MES INVENTOR -J. R. STACK ATTOR Y Patented June 16,1942 REFINING or NONFERROUS METALS James R. Stack, Staten Island, N. Y.,asslgnor to Nassau smelting & Refining Company, Incorporated, New YorkYork, N. Y., a corporation of New Application March 21, 1938, Serial No.197,209

19 Claims.

This invention relates to the refining of nonferrous metals and moreparticularly to the refinishing of copper bearing materials.

Considerable quantities of scrap materials containing substantialamounts of copper and lesser amounts of tin, lead, zinc, iron and othermetals are obtained from discarded materials, such as used telephone andother electrical equipment, machine shop turnings, refinery and foundryscraps and materials from various other sources. Efforts have been madeheretofore to refine these low grade materials to obtain the constituentmetals therefrom in usable forms.

In one process which has been used heretofore, the impure material ischarged into a blast furnace and smelted to remove the major portiontory furnace and is further refined by blowing and poling, after whichit is cast into anodes which are electrolytically refined in a standardsulphuric acid electrolyte. The principal objections to this process arethat the metal must be carried through a number of refining steps inorder to obtain pure copper 'and the bag house dust or fume containingthe lead, tin and zinc is difiicult to treat to recover the constituentmetals.

In another process which has been practiced previously, the scrapmaterial is treated in a blast furnace to eliminate the iron and theresultant molten metal is charged into a converter where substantiallyall of the zinc only is removed by blowing with air. The metal from theconverter is cast into anodes and is electrolyzed for the production ofcopper in a sulphuric acid electrolyte of relatively low concentration.During the electrolysis most of the metals other than copper, such aslead and tin, are converted into insoluble compounds, and some of thesecompounds adhere to the anodes, some remain suspended in the electrolyteand the balance fall to the bottom of the electrolytic cell in the formof anode slimes. Any dissolved antimony is rendered insoluble as anoxychloride by the presence of chlorine ions, previously added to thesolution, or by other known means. The anode slimes produced are treatedto recover the metallic values therein. Among the objections to thisprocess are the high cost of the electrolytic refining due to theabnormally high cell voltage necessitated by the low conductivity of theelectrolyte and the large amount of slimes produced. Furthermore, it isvery difiicult to treat these slimes to separate and recover the variousmetals contained therein. These slimes also interfere with the operationof the cell and in addition carry considerable quantities of copper downwith them.

Among the objects of the present invention are the provision of aneffective and economical method of refining low grade copper bearingmaterials to obtain theprincipal constituents thereof in usable formsand the provision of electrolytic processes for separation of metalssuch as copper, lead, tin and zinc without the production of largeamounts of slimes.

This application is a continuation in part of copending applicationSerial No. 91,298, filed July 18, 1936, by the present inventor, andupon which United States Patent 2,111,575 was issued on March 22, 1938.

In accordance with one embodiment of the invention anodes, consisting oflow grade copper material containing relatively large amounts'of lead,tin, zinc and the like together with smaller amounts of other metallicimpurities such as arsenic, antimony, iron, nickel, etc., may beelectrolyzed for the production of pure copper cathodes in a bath freefrom sulphuric acid or sulphates or halogen compounds other thanchloro-sulphonic acids and having enact the aromatic sulphonic acids orone of the related chloro-sulphonic or nitro-sulphonic acids of aromatichydrocarbons, as the principal active electrolytic agent, e. g.phenol-sulphonic acid, benzene disulphonic acid, or the like.

In all cases of such electrolysi it is possible to obtain cathodes ofsubstantially pure copper, free from any of the originally admixedmetals.

The resulting liquor then may contain lead, tin and copper in amounts ofroughly the same order together with other impurities in smalleramounts. The bulk of the remaining copper may be removed by electrolysiswith insoluble anodes and the rest of the copper by cementing or directreplacement with metallic tin or lead 'or both.

The now copper free liquor may then be electrolyzed to deposit out thetin or lead or both simultaneously (if both are present) as electrolyticsolder, and thus the bulk of the original content of copper, tin andlead is recovered in useful forms.

After this removal of tin and lead, the liquor may be evaporated toremove the greater portion of its metallic salts content bycrystallization and the resulting strong acid returned to the beginningof the process to re-enter the sulphonic acid electrolyte, while thesalts comprising chiefly sulphonates of zinc and nickel are worked up toseparate and recover thes metals by any suitable method as well a torecover the sulphonic acid for return to the process.

The above described and other objects and features of the invention willbe more apparent from the following detailed description thereof takenin conjunction with the accompanying drawings, in which i Fig. 1 is adiagrammatic and skeleton flow sheet of a process embodying theinvention;

Fig. 2 is a similar flow sheet of another form; and

Fig. 3 is a similar flow sheet of a third form.

In one specific embodiment of the invention, impure copper bearingmaterials from any suitable sources are charged into a blast furnacealong with limestone and coke and the material is smelted to eliminatemost of the iron in the form of a slag. The slag, which will also carrywith it a portion of the zinc found in the material, is discarded. Someof the zinc is volatilized in the blast furnace and may be recovered, ifdesired.

The copper bearing materials charged into the blast furnace may be ofvaried types and compositions. The charge may comprise junked electricalapparatus containing brass, bronze, iron, copper, lead, solder, germansilver, chromium, nickel, aluminum, zinc, and various non-- metallicmaterials, principally insulating materials, such as rubber, porcelain,wood, slate, phenol plastics, silk, cotton, paper, cellulose esters,lacquers, enamels, etc. The charge may also include or consist of othercopper bearing scraps and junked materials, machine shop sweepings, andmiscellaneous refinery and foundry scraps, slags, ashes, etc. Typicalmaterials suitable for use in this process might contain from about to60% copper, 0.5 to 20% tin, .5 to 20% lead, and the balance principallyiron, zinc, and non-metallic materials. The process is also applicableto the refining of materials which are free from either lead or tin,although most materials of the type described contain both of thesemetals,

In the blast furnace, the combustible materials in the charge will beconsumed, while some of the metallic impurities, such as chromium andaluminum, will be substantially eliminated in the slag. Other metallicimpurities, for example, nickel, will enter the pig metal produced inthe blast furnace, but they will not interfere with the subsequentoperations.

The pig metal taken from the blast furnace contains practically all ofthe copper, tin and lead and a substantial part of the zinc found in theoriginal material. This metal'is transferred in the molten statedirectly to an oil fired converter, r it may be cast into pigs which arestored and later melted andcharged into the converter. In the converter,some silica is added and substantially the remainder of the zinc isremoved from the metal by blowing air therethrough. Since iron and zincboth oxidized more readily than do lead and tin, and zinc is morevolatile than lead and tin, the iron and zinc will be removed first fromthe metal in the converter either as oxides which enter the converterslag or, in the case of zinc, as a vapor which oxidizes very readilyinto zinc fume. Consequently, the converter charge is blown until thezinc is substantally all eliminated either as fume, or in the slag, andthe process is stopped before much of the lead and tin is removed. The

point in the process where the zinc is almost completely exhausted andthe lead and tin begin to be removed from the metal may be determined bywatching the flame at the mouth of the converter, since a noticeablechange in the appearance of the flame takes place at this point. Othermeans of determining this point may, of course, be used if desired. Thezinc oxide fumes produced in the blast furnace and converter areconveyed to a bag house where they are collected in the form of a dustconsisting principally of zinc oxide, which may be sold as such. Theslag formed in the converter, which contains the iron and a substantialportion of the zinc formerly found in the metal charged into theconverter, is removed after the metal has been blown, and is returned tothe blast furnace.

The blown converter metal is cast directly into anodes which consistprincipally of copper, tin and lead, but which may contain minorquantities of such metals as zinc, antimony, nickel and iron. Theseanodes are then electrolyzed for the production of electrolytic coppercathodes in an electrolyte which will form soluble salts of copper, leadand tin. .Anodes produced by treating junked telephone equipment mightcontain from 70 to 95% copper, .5 to 15% tin, .5 to 15% lead, and theremainder a mixture of small amounts of other metals. A typical anodeobtained from materials of the type referred to above comprisedsubstantially copper, 3.5% tin, 5% lead, .5% zinc, and the remainderother metals, such as antimony, nickel and iron.

It will, of course, be obvious that if the original material to berefined is substantially free from either iron or zinc, the stepemploying the blast furnace or the converter will be omitted, andlikewise that both of these operations will be unnecessary if both ironand zinc are substantially absent. The invention is also not limited tothe removal of the iron and zinc by smelting in a blast furnace, andblowing in a converter, as described. Any convenient methods well knownin the art may be used to eliminate the iron and zinc, provided they donot remove the copper, lead and tin in sufficient quantities to renderthe process uneconomical. For example, the scrap material may be chargedinto a reverberatory furnace, and the iron removed by liquation or as aslag, while the zinc is removed as a slag and/or a fume. This procedureis particularly applicable when the scrap material is relatively freefrom inert and non-metallic materials. In any event, the material,either purified or in its original state, is cast into anodes when itconsists essentially of copper, lead and tin.

Among the materials which are particularly suitable for use aselectrolytes in the refining of the anode metal are the aromaticsulphonic acids and very satisfactory result may be obtained byemploying a sulphonic acid such as phenol sulphonic acid or benzenedisulphonic acid in which copper, lead, tin, zinc, iron and nickel areall soluble. The various chloro-sulphonic and nitro-sulphonic acids mayalso be applied to this use. It is'furthermore found that, especiallywhen lead i present, an absence of any appreciable amount of sulphuricacid or of sulphates is preferable.

In carrying out one process embodying the present invention, anelectrolytic bath is made up containing about 350 to 500 grams ofbenzene disulphonic acid per liter. Copper is then dissolved into thissolution, preferably electrolytically, until 9 to 50 grams per liter. ofcopper at pesent. The free acid in the bath will then range from 290 to410 grams per liter. The above has been found to be a satisfactory andsimple method of preparing a bath according to the present invention,but other methods which have substantially the same resulting productmay well be used, ea 8- dissolving 290 to 410 grams per liter of theacid and a sufficient quantity of previously prepared copper salt of theacid to provide 9 to 50 grams of copper per liter.

Anodes for use insuch a bath may typically consist principally of coppercontaining tin and lead as primary impurities but which may also includesmaller amounts of nickel, zinc, arsenic, antimony. iron, etc.

Such anodes are electrolyzed in the bath described, preferably usingcopper starting sheets as cathodes. Preferably, the electrolyte iscirculated during the electrolysis, although rotating anodes or cathodesor the like means, such as stirrers, may also be used, and, alsopreferably, the temperature of the bath will be maintained at from 60 to82 0., although the procedure operates satisfactorily under someconditions within the range of from 40 to 90 C. or even beyond this.

Depending somewhat upon the composition of the anodes actually used atany given time, as well as upon the composition of the bath, and alsoconditions of temperature, the current density will preferably run from8 to 25 amperes per square foot, and the cell voltage from 0.15 to 0.35volt.

In a given illustrative instance in which the procedure shown in Fig. 1may be followed, an electrolyte containing no oxidizing agents andnickel free crude anodes may be used. The following is a typical anodecomposition, the weight used being 2128 lbs.

Type I Per ,cent Copper 86.0 Lead 7.0 Tin 5.0 Arsen 0.1 Antimony 0.2Iron 01 Nickel 0.0 Zinc 1.0

"Per cent pp 43.0 Tin 17.4 Lead 6.5 Antimony 4.0

These slimes are disposed of substantially in a manner hereinafterdescribed.

The foul electrolyte after this step should show a metal content ofabout Grams per liter Copper 16 Lead 1- 28 Tin 16 Zinc 8 Free acid 300 Aportion of this liquor is removed and replaced with fresh solution, andthis liquor is treated electrolytically with insoluble anodes to removecopper down to about the point where other metals would begin todeposit, thus producing a further relatively small amount (about 70lbs.) of copper. The liquor is then treated with tin to deposit outcopper by replacement and to reduce stannic tin in the solution to thestannous form. This produces roughly 20 lbs. of copper cement" whichcould be returned to the production of crude anodes or roasted and usedin the preparation of electrolytic solution for the first step.

The resultant liquor is substantially copper free and contains aboutGrams per liter This is then electrolyzed with insoluble anodes todeposit the lead and tin together as electrolytic solder and producessome 310 lbs. of solder showing about 45% lead and 55% tin.

The original crude anodes being thought of as substantially free fromnickel, the liquor now to be considered is practically a solution onlyof zinc sulphonate and free sulphonic acid. This may be concentrated byevaporation to crystallize out the zinc sulphonate. The mother liquormay be returned to the preparation of electrolyte. The zinc salt may bere-crystallized if necessary, dissolved, and treated with lime, thusprecipitating the zinc out as hydroxide. The calcium sulphonate solutionupon treatment with a quantitative amount of sulphuric acid toprecipitate the calcium as calcium sulphate yields free sulphonic acidto be returned to the cycle, The zinc is recovered from the hydroxide byleaching with caustic soda and electrolysis of the sodium zincatesolution. l

The original electrolyte may well be charged with copper by using arelatively high grade copper scrap, clippings, turnings,'punch scrap,scrap wire, or the like.

In this particular example, the original electrolysis of step 1 is donein an open topped tank, with the surface of the electrolyte exposed tothe atmosphere, and with the electrolyte circulated, thus exposing allof the solution to the oxygen of the air. In the case of nickel freecrude anodes like Type I, this exposure to the air is usuallyunimportant. If there is nickel present and the air is given free accessto the circulated electrolyte in step 1, the procedure changesmaterially in the effected. results, as will appear from the followingillustrative procedure, which also follows the general outline of Fig.1.

In this instance the crude anodes may be thought of as generally likeType I, but comprising also some nickel. For example, the followingcomposition will be termed Type II.

Except as instanced below, the process and its results are substantiallythe same as those de- Lea 28 Ti 2 Nickel 2 Zinc 8 Free acid 300 Theanode slimes of step 1, on the other hand, amount to about 12% of theweight of the anodes consumed, or twice as much as in the case of TypeI, and show a metal content such as the following:

Per cent Copper 20 T 41 Lead 3 Antimony 2 Thus, with no nickel or oxygencontaining oxidizing agent present (type I) the bulk of the tin remainsdissolved in the electrolyte and accompanies the lead through step 3 tobe recovered, without separation from the lead, as electrolytic solder,while with nickel present and the bath exposed to the air 90% or more ofthe anodically dissolved tin from the crude anodes goes into the anodeslimes and the lead continues on as before.

Hence in step 2, although tin, lead or solder may be used to cement outthe residual copper, it may be preferred to use only lead with theresult that at step 3, the cathodes produced are principally lead,running in some cases upward of 95% lead and the small balance tin. Infact, experimental work shows that in some cases at least, properbalancing of conditions in step I will result in driving practically allof the tin into the slimes, thus effecting a substantially cleanseparation in one step at this stage of the lead and tin from eachother, tin into the slimes, and lead into the electrolyte.

Also in the process now being considered, it may be preferable toprepare the original electrolyte for step I with a certain minimumcontent of nickel necessary to act from the beginning of theelectrolysis as a catalyte to efiect the oxidation and precipitation ofthe tin as soon as its anodic solution begins. To this end theelectrolyte will be compounded to contain sulphonic acid and coppersulphonate as already described, and will also have enough nickelintroduced, by 'anodic solution of metallic nickel or by solution ofnickel sulphonate or otherwise, to effect in the electrolyte a contentof enough nickel to give the desired eilect, in the present instanceabout 2 grams per liter.

It is found that if access of air to the bath in step I is prevented, asby floating a thick layer (one or more inches) of oil on the surface,the eilect of the nickel is partly inhibited, and nickel bearing anodessuch as type II can be treated according to the scheme described abovefor the treatment of nickel free material such as anodes of type I.Then, however, the amount of tin in the slimes is greater than whennickel is absent.

If it be desired to separate the tin cleanly, in the absence of nickelto oxidize the tin catalytically, this may be accomplished by adding tothe bath a direct oxidizing agent which will not effect the procedureinjuriously in other respects. Thus hydrogen peroxide .will give asubstantially quantitative precipitation of the tin in the slimes. aswill also barium peroxide, lead peroxide, and other suitable agents. Thedecomposition product of hydrogen peroxide is water, which helps tooffset evaporation from the bath. The lead from lead peroxideaccompanies the anodic lead and is removed at step 3. Barium from bariumperoxide will continue, inertly so far as the process is concerned, Inthe liquor, to mix with the calcium waste at the end.

In the procedure of Fig. 1 and in the absence of nickel, this may wellbe done between steps I and 2 or between steps 2 and 3, by addingsubstantially the theoretically quantitative amount of a suitablesolution, for example, of hydrogen peroxide, required to precipitate thetin present in the form of metastannic acid. 'In such case, of course,only lead and not tin will be used to cement out copper in step 2 andthe cathodes produced in step 3 will be substantially pure lead and nota solder or lead-tin alloy.

If the procedure of step I of Fig. 1 be carried out in the presence ofnickel but in the absence of air, as by blanketing the surface of thebath with inert oil, obviously tin may be removed, as just described,between steps I and 2 or between steps 2 and 3, by means of an oxidizingagent.

Also if, when nickel is present and air Is admitted to drive tin intothe slimes, it is desired to produce substantially pure lead cathodes atstep 3 instead of low tin solders, the residual tin in the solutionafter copper is cemented out with lead in step 2 may be precipitated asdescribed. Or oxidizing agent may be added to the bath originally.

A somewhat'difierent procedure embodying the invention is that of Fig.2. Here anodes of either type are electrolyzed as in either of theseveral above described procedures in step I, and the anode slimesseparated for treatment as hereinafter described.

The foul electrolyte containing some copper, lead, tin, zinc and minoramounts of other metals is treated with the quantitative amount ofsulphuric acid required to precipitate all the lead as lead sulphate.This is removed from the liquor to be disposed of as such or to beworked up in any suitable manner to recover the lead as metal.

The resulting liquor may then be electrolyzed with insoluble anodes tofree the solution of residual copper and tin, the cathodes and sludgeproduced here being returned to the production of crude copper anodes,while the liquor is precipitated with lime. Zinc is leached from theprecipitated hydroxide with caustic soda and recovered as before. Thecalcium sulphonate solution. is worked up to recover sulphonic acid.Nickel is recovered from the soda leached residues in any suitablemanner.

In this procedure also, it may be preferred to separate tin, asdescribed above, by precipitation as metastannic acid with an oxidizingagent such as hydrogen peroxide. This may beconveniently done in themanner described between steps I and 2 or between steps 2 and 3.

In the parent application mentioned above, of which the present is acontinuation in part, there is disclosed a variety of sulphonic,chloro-sulphonic and nitro-sulphonic acids and the like, which aresuitable for use as electrolytes for the separation of metals,substantially in the manner herein described, whereas in the abovedescription of the present application only benzene disulphonic acid isspecified. Benzene disulphonic acid is at present the preferred memberof the class of electrolytes mentioned, but the above procedures are notintended to be limited to the use of this acid alone. The specificprocedures are illustrative only and will require no essentialalteration or modification in case another of the electrolytes inquestion is used in place of benzene disulphonic acid.

In each of the above procedures, the first step of electrolyzing thecrude copper anodes in the sulphonic acid electrolyte produced an amountof anode slimes which was merely set aside 1 for future consideration.These are now to be taken.

any approvedmanner and furnace and are cast into anodes, which in oneillustrative instance showed the following composition upon analysis:

Per cent Tin a 80 Lead 13 Antimony 4 Copper 2 Other admixtures 1 For theelectrolysis of such materials it is preferable to use phenol sulphonicacid free from sulphuric acid and sulphates although benzene disulphonicacid is also suitable. In practice, the phenol sulphonic acid employedmay be the purified product of the direct sulphonation of phenol,containing a mixture of mono and disulphonated phenol with perhaps smallamounts of even higher sulphonation products, and in which may bepresent any one or two or all three of the di-acids. A preferred bathfor this electrolysis will contain from about 150 to about 350 grams perliter of the phenol sulphonic acid. The bath is improved for theproduction of good cathodes by the addition of such agents as glue,resorcinol or the like. In one instance the addition to the bath of fromabout 0.075 to about 0.10 gram per liter each of glue and resorcinol wasfound to improve materially the mechanical quality of the cathodes.

This electrolysis produces substantially pure cathodes of tin, solder orlead according to the composition of the anodes used, in which tin orlead may vary from nothing to over 80%. In installation in localitieswhere power is relatively costly, it is preferable that the anodescontain not over about 12% of antimony, copper and other admixturestaken together. The process canbe successfullyoperated when power ischeap with anodes containing as much as 40% of these materials but onlyat the cost of excessive cell voltages and eventual electrodepolarization. Substantially 'all of the antimony, copper and otheradmixtures, together with sometin and lead, comes out as anode slimeswhich may be treated in any suitable manner to recover their components,

While this procedure, diagrammed in Fig. 3, is described as applied tothe anode slimes of step I in Figs. 1 and 2, it is obviously notconfined to such slimes as a starting point, but may be applied as anindependent procedure to materials of suitable compositions derived fromany source. For example, such a procedure may be of value in thetreatment of such materials as scrap solder, lead alloy cable sheathscrap, and the like.

The aromatic sulphonic acids are preferably used in the electrolyte incarrying out the electrolytic steps in the refining process embodyingthe invention for several reasons. In the first place, they dissolve notonly the copper but also the lead and tin. In addition, they have a highconductivity, they are relatively non-volatile, and are not appreciablydecomposed electrolytically. They, therefore, permit the electrolyticdeposition of pure copper without the precipitation of substantialquantities of the lead and tin as slimes. Their high conductivity lowersthe power consumption and their stability makes them economical to usebecause they may be recovered and reused.

Among the aromatic sulphonic acids which may be employed are the monovand poly sulphonic acids of phenol, benzol (benzene), tuluol (tuluene)the cresols, the xylenes, the xylenols, naphthalene, the naphthols,-anthracene, phenanthrene, and related compounds. The related chloro andnitro sulphonic acids of aromatic hydrocarbons may,'likewise, be used.In addition, satisfactory results may be obtained by using the sulphonicacids of aliphatic compounds like methane, ethane, propane, etc.Mixtures of these acids may, of course, be used if desired.

Since the acids mentioned above dissolve'coppe'r, lead and tin, it isobvious that the invention may be practised to refine copper bearingmetals that include either one or both of lead and tin. For example,scrap brasses may contain no tin, while bronzes may be free from lead.These materials may be carried through the refining steps described inthe same manner that is employed for materials containing both lead andtin, the only difference being that the products obtained would notinclude lead or tin, as the case may be.

It may further be noted that in the procedures where no direct oxidizingagent, e, g. hydrogen peroxide, or catalytic oxidizing agent, e. g.,nickel, is used, and it is desired to keep the production of anodeslimes to a minimum, especially as regards those due to tin, it may beof advantage to use an inert oil to blanket the surface of the bath andthus prevent access ofatmospheric oxygen to the bath. Since the bath maybe strongly agitated by a circulation pump, stirrers, moving electrodesor the like, this oil cover may need to be comparatively thick, e. g,one or two inches or more. Oils suitable for this purpose are, for ex-In operations according to the several procedures outlined in connectionwith Figs. 1 and 2, in step i, in view of the fact that neither the leadnor the tin is deposited at the cathode, these metals will graduallyincrease in concentration in the electrolyte and will eventually renderthe electrolyte ineffective for the deposition of pure copper.Consequently, a portion of the solution is removed from time to time andthe lead and tin present therein are removed. The ensuing steps 2, 3etc., are to be thought of ordinarily as carried out upon these removedportions of the electrolyte of step I. In this manner the processes inquestion are made continuous, for the copper content is kept constant inthe electrolyte of step I and sufllciently high so that only copper isdeposited on the cathodes in this step, the constantly increasingcontent of metals of the group consisting of lead and tin and zinc beingperiodically brought down by this replacement of portions of the foulelectrolyte with fresh solution. Thus, ordinarily, in the drawings aswell as in the speciflcation, the phrase foul electrolyte is intended tomean such withdrawn portions of the electrolyte of step i. If desired,however, these procedures can be operated in batch fashion, wherein,when the electrolyte of step I becomes too loaded with other metals toeifect deposition of pure copper, the entire volume is transferred tostep 2 and replaced by fresh solution for step I.

The molecular or atomic mechanics of the actions of nickel in effectingincreased precipitation of tin in the anode slimes of Fig. 1 is not asyet clearly understood. It behaves, however, as if it were a carrier orcatalyte to effect oxidation of tin with oxygen from the air. In thisapplication, the phrases catalytic: agent, "catalytic oxidation agentand the like are to be taken to mean substances which effect thisoxidation in the manner that nickel does and which themselves contain nooxygen, whereas phrases like "chemical agent, chemical oxidizing agent,"direct oxidizing agent" and the like are to be taken to mean oxygenbearing oxydants such as hydrogen peroxide,barium peroxide, leadperoxide and the like.

In step I of Figs. 2 and 3, when nickel is present in the crude anodesand the process is started with a nickel free electrolyte, nickel willbuild up in the solution and begin an increasing catalytic effect. If itbe desired to throw out tin in the anode slimes, this may obviously beaccomplished by adding diminishing amounts of direct oxidizing agentfrom the beginning (e. g. hydrogen peroxide) until the nickel issufllciently built up to act alone.

It will be clear from the foregoing that a principal feature of thepresent invention is the discovery that in such electrolytic baths asare described hereinabove, the anodlically dissolved tin may be causedto divide itself in substantially any desired ratio between dissolvedtin remaining in the bath and tin precipitated as anodic slimes, whilethe lead remains in solution. This is accomplished by maintaining in thebath a predetermined degree of oxidizing effect which can be created andmaintained by addition of catalytic oxidizing agent, by addition ofchemical oxidizing agent, or by any convenient combination of theseagencies.

From the foregoingdescription, it is apparent that the inventionprovides simple, effective and economical processes for refiningnon-ferrous metals. It also provides new and improved electrolytes andelectrolytic processes for the separation of metals, including copper,lead and tin.-

Various modifications and changes may, of course, be made to adapt theinvention to varying conditions. Hence, the invention is not limited tothe specific embodiments described herein, but embraces allmodifications and equivalents falling within the scope of the annexedclaims.

What is claimed is: v1. The method of separating metals fromtincontaining metallic materials consisting principally of copper, whichcomprises electrolyzing anodes of such a material in a bath having asulphonic acid as principal electrolytic agent to deposit substantiallypure copper, and causing an oxygen-bearing oxidizing agent tending topromote precipitation of tin as anode slimes to'be present in the bathduring the electrolysis in -sufiicient amount to effect theprecipitation as anode slimes of a material quantity of tin which wouldotherwise be held in solution.

2. The method of separating metals from tincontaining metallic materialsconsisting principally of copper, which comprises electrolyzing anodesof such a material in a bath having an aromatic sulphonic acid asprincipal electrolytic agent to deposit substantially pure copper, andcausing hydrogen peroxide to be present in the bath during theelectrolysis in suiiicient amount to effect the precipitation as anodeslimes of a material quantity of tin which would otherwise be held insolution.

3. The method of separating metals from tincontaining metallic materialsconsisting principally of copper, which comprises electrolyzing anodesof such a material in a bath having an aromatic sulphonic acid asprincipal electrolytic agent to deposit substantially pure copper, and.causing lead peroxide to be present in the bath during the electrolysisin sufficient amount to effect the precipitation as anode slimes of amaterial quantity of tin which would otherwise be held in solution.

4. The method of separating metals from tincontaining metallic materialsconsisting principally of copper, which comprises electrolyzing anodesof such a material in a bath having benzene dlsulphonic acid asprincipal electrolytic agent to deposit substantially pure copper, andcausing an oxygen-bearing oxidizing agent tending to promoteprecipitation of tin as anode slimes to be present in the bath duringthe electrolysis in sufllcient amount to effect the precipitation asanode slimes of a material quantity of tin which would otherwise be heldin solution.

5. The method of separating metals from metallic materials consistingprincipally of metal of the group consisting of tin and lead andcontaining copper as a substantial but minor constituent, whichcomprises forming anodes of such a material, and electrolyzing theanodes in a bath having at least grams per liter of phenol sulphonicacid as principal electrolytic agent to deposit substantially pure metalof the group consisting of tin and lead.

6. The method of separating metals from metallic materials consistingprincipally of metal of the group consisting of tin and lead andcontaining up to about 12% of other admixtures including copper as asubstantial constituent, which comprises forming anodes of such amaterial, and electrolyzingthe anodes ina bath having from about 150grams per liter to about 350 grams per liter of phenol sulphonic acid asprincipal electrolytic agent to deposit substantially pure metal of thegroup consisting of tin and lead.

7. The method of separating metals from metallic materials consistingprincipally of copper and containing metal of the group consisting oftin and lead, which comprises forming anodes from such a mixture,electrolyzing the anodes in a bath having benzene disulphonic acid asprincipal electrolytic agent to deposit substantially pure copper,preparing metallic anodes from the anode slimes produced, andelectrolyzing the second named anodes in a bath having phenol sulphonicacid as principal electrolytic agent to deposit substantially pure metalof the group consisting of tin and lead.

8. The method of separating metals from tincontaining metallic materialsconsisting principally of copper, which comprises forming anodes of sucha material, electrolyzing the anodes in a bath having from about 350 toabout 500 grams per liter of the acid radical of benzene disulphonicacid as principal electrolytic agent to deposit substantially purecopper, and causing an oxygen-bearing oxidizing agent tending to promoteprecipitation of tin as anode slimes to be present in the bath duringthe electrolysis in sufflcient amount to effect the precipitation asanode slimes of a material quantity of tin which would otherwise be heldin solution.

9. The method of separating metals from tincontaining metallic materialsconsisting principally of copper, which comprises forming anodes of sucha material, electrolyzing the anodes in a bath having from about 290 toabout 410 grams per liter of free benzene disulphonic acid and fromabout 9 to about 50 grams per liter of dissolved copper as principalelectrolytic agents to deposit substantially pure copper, causing anox-- ygen-bearing oxidizing agent tending to promote precipitation oftin as anode slimes to be present in the bath during the electrolysis,and regulating the concentration of the agent in the bath so as tomaintain substantially throughout the electrolysis a predetermined ratiobetween tin precipitated as anodes slimes and tin dissolved in the bath,the tin precipitated as anode slimes comprising a material quantity oftin which would otherwise be held in solution.

10. The method of separating metals from tincontaining metallicmaterials consisting principally of copper, which comprises forminganodes of such a material, electrolyzing the anodes in a bath having anaromatic sulphonic acid as principal electrolytic agent to depositsubstantially pure copper, causing an oxygen-bearing oxidizing agenttending to promote precipitation of tin as anode slimes to be present inthe bath during the electrolysis, and regulating the concentration ofthe agent in the bath so as to maintain substantially throughout theelectrolysis a predetermined ratio between tin precipitated as anodeslimes and tin dissolved in the bath, the tin precipitated as anodeslimes comprising a material quantity of tin which would otherwise beheld in solution.

11. The method of separating metals from tincontaining metallicmaterials consisting principally of copper, which comprises forminganodes of such a material, electrolyzing the anodes in a bath having anaromatic sulphonic acid as principal electrolytic agent to depositsubstantialy pure copper, causing hydrogen per-.

oxideto be present in the bath during the elec trolysis to promoteprecipitation of tin as anode slimes, and regulating the concentrationof the hydrogen peroxide in the bath so as to maintain substantiallythroughout the electrolysis a predetermined ratio between tinprecipitated as anode slimes and tin dissolved in the bath, the tinprecipitated as anode slimes comprising a material quantity of tin whichwould otherwise be held in solution.

12. The method of separating metals from tincontaining metallicmaterials consisting principally of copper, which comprises forminganodes of such a material, electrolyzing the anodes in a bath having anaromatic sulphonic acid as principal electrolytic agent to depositsubstantially pure copper, causing lead peroxide to be present in thebath during the electrolysis to promote precipitation of tin as anodeslimes, and regulating the concentration of the lead peroxide in thebath so as to maintain substantially throughout the electrolysis apredetermined ratio between tin precipitated as anode slimes and tindissolved in the bath, the tin precipitated as anode slimes comprising amaterial quantity of tin which would otherwise be held in solution.

13. The method of separating metals from tincontaining metallicmaterials consisting principally of copper, which comprises forminganodes of such a material, electrolyzing the anodes in a bath havingbenzene disulphonic acid as principal electrolytic agent to depositsubstantially pure copper, causing hydrogen peroxide to be present inthe bath during the electrolysis to promote preciptation of tin as anodeslimes, and regulating the concentration of the hydrogen peroxide in thebath so as to maintain substantially throughout the electrolysis apredetermined ratio between tin precipitated as anode slimes and tindissolved in the bath, the tin precipitated as anode slimes comprising amaterial quantity of tin which would otherwise be held in solution.

14. The method of separating metals from tincontaining' metallicmaterials consisting principally of copper, which comprises forminganodes of such a material, electrolyzing the anodes in a bath havingbenzene disulphonic acid as principal electrolytic agent to depositsubstantially pure copper, causing lead peroxide to be present in thebath during the electrolysis to promote precipitation of tin as anodeslimes, and regulating the concentration of the lead peroxide in thebath so as to maintain substantially throughout the electrolysis apredetermined ratio between tin precipitated as anode slimes and tindissolved in the bath, the tin precipitated as anode slimes comprising amaterial quantity of tin which would otherwise be held in solution.

15. The method of separating metals from tincontaining metallicmaterials consisting principally of copper, which comprises forminganodes of such a material, electrolyzing the anodes in a bath having anaromatic sulphonic acid as principal electrolytic agent to depositsubstantially pure copper, causing an oxygen-bearing oxidizing agenttending to promote precipitation of tin as anode slimes to be present inthe bath during the electrolysis, and regulating the concentration ofthe agent in the bath so as to effect the maximum precipitation as anodeslimes of tin which pure copper, causing an oxygen-bearing oxidizingagent tending to promote precipitation of tin as anode slimes to bepresent in the bath during the electrolysis, and regulating theconcentration of the agent in the bath so as to maintain substantiallythroughout the electrolysis a predetermined ratio between tinprecipitated as anode slimes and tin dissolved in the bath, the tinprecipitated as anode slimes comprising a material quantity of tin whichwould otherwise be held in solution.

18. The method of separating metals from metallic materials consistingprincipally of copper and containing metal of the group consisting oftin and alloys of lead and tin, which comprises forming anodes of such amaterial, electrolyzing the anodes in a bath having benzene disulphonicacid as principal electrolytic agent to deposit substantially purecopper, causing an oxygen-bearing oxidizing agent tending to promoteprecipitation of tin as anode slimes to be present in the bath duringthe electrolysis in sufllcient amount to effect the precipitation asanode slimes of a material quantity of tin which otherwise would be heldin solution, forming metallic anodes from the anode slimes, andelectrolyzing the last named anodes in a bath having phenol sulphonicacid as principal electrolytic agent to deposit tin substantially freefrom any admixture except lead.

19. The method of separating metals from metallic materials consistingprincipally of copper and containing metal of the group consisting oftin and alloys of lead and tin, which comprises forming anodes of such amaterial, electrolyzing the anodes in a bath having benzene disulphonicacid as principal electrolytic agent to deposit substantially purecopper, causing an oxygenbearing oxidizing agent tending to promoteprecipitation of tin as anode slimes to be present in the bath duringthe electrolysis, regulating the concentration of the agent in the bathso as to maintain substantially throughout the electrolysis apredetermined ratio between tin precipitated as anode slimes and tindissolved in the bath, the tin precipitated as anode slimes comprising amaterial quantity of tin which would otherwise be held in solution,forming metallic anodes from the anode slimes, and electrolyzing thelast named anodes in a bath having phenol sulphonic acid as principalelectrolytic agent to deposit tin substantially free from any admixtureexcept lead.

' JAMES R. STACK.

